INDUCTION OF TRIPLOIDY IN WALLEYE Sander vitreus AND EVALUATION OF GROWTH DIFFERENCES BETWEEN TRIPLOID, CONTROL, AND HYBRID WALLEYE

Walleye are native to most rivers and natural lakes in the Midwestern United States, as well as most of Canada and have been introduced through stocking into most man-made lakes due to their high value as both a sport and commercial species. Walleye propagation and stocking programs are a major focus of various fisheries management agencies; however,  development of this species in the aquaculture industry has been limited. Induction of triploidy has long been used as a sterilization method across fish species and has proved a valuable tool used by management agencies to preserve genetic integrity of natural stocks. The objective of this study is to optimize production of triploid walleye and compare growth and survival to that of control and hybrid walleye in order to enhance the walleye aquaculture industry.

Gametes were collected from wild Maumee River walleye and sauger and transported back to the laboratory in Columbus, OH, where we conducted in vitro fertilizations. Three different pressure shocks applied at 4min post fertilization were evaluated for efficiency of producing triploid walleye: 1) 7000PSI, 40min duration, 2) 8000PSI, 30min duration, and 3) 9000PSI, 12min duration. Control and hybrid walleye were produced alongside. Fertilization rates differed between shock groups, with 65.6% in 7000PSI, 28.2% in 8000PSI, and 53.9% in 9000PSI, while fertilization rates for hybrid and control walleye were 28% and 23.1%, respectively. Mortality in the 7000PSI shocked group reached 100% at 10 days post fertilization (dpf), when the other groups were hatching.  Triploidy in the 8000 and 9000 PSI shock groups were induced at rates of 68.8%, and 95%, respectively. At 18dpf, fish from control, hybrid, and highest surviving triploid group, 9000PSI, were stocked to aquaria, (260fish/tank) in duplicate, in a closed recirculation system maintained at 3ppt salinity. Fish were fed live Artemia nauplii as first food and algal paste provided turbidity. Fish were sampled after 10 and 17d of feeding.  After 17d of feeding, the 2 aquaria for each group were combined and then randomly stocked to two 60L flow-through tanks (100 fish/tank).  Fish continued to be fed live Artemia, until they were transitioned to dry diet at 40d of feeding.  A subsample (n=10) of fish from each of the six 60L tanks were measured at 105d of feeding (122dpf). Mean weight and length data from 10, 17, and 105d of feeding are presented in Table 1. Fish continued to be grown and weight, length, and survival monitored.